Once or twice a week taskhost.exe slows my computer to a halt! It takes up 25% of my CPU power (ie. 1 processor). I can't kill it an have no idea what it is doing. I imagine that its some kind of window's scheduled activity.

The path of taskhost.exe is simply: "taskhost.exe $(Arg0)". I've downloaded and run the latest Microsoft Security Essentials and it detected no viruses.
–
user145395Nov 14 '12 at 22:15

What windows version are you running? Do apply all patches from MS?
–
John SiuNov 15 '12 at 3:06

Yes system is up to date. I actually just figured this out finally. About to post an answer.
–
user145395Nov 15 '12 at 19:51

#2 is extremely useful, thanks. I am using Windows 8, it's a little different there - open task manager, tab 'Processes', right click on the column headers, then check the command line column.
–
Martin HansenSep 7 '14 at 12:23

Turns out this was caused by the "RacTask" (Reliability Analysis Custom Handler). I used the Task Scheduler to view "All Running Tasks" and then killed it from there. The problem was immediately addressed.

In my case, the task seemed to have something to do with Microsoft Customer Experience Improvement Program. (Ironic). It seems to me it was connected in someway with uploading customer configuration data to Microsoft. If so, seems harmless to disable.

Summary: run taskschd.msc, locate Microsoft/Windows/RAC, disable it using GUI.